1. Field of the Invention
The present invention relates generally to a filtering material employable for various kinds of application fields, e.g., a sanitary filter, a deodoring filter incorporated in a various kind of deodoring unit, and a foodstuff packing material having a capability of sterilizing and deodoring. More particularly, the present invention relates to a filtering material having a function for effectively and reliably adsorbing very fine infectious or antigenous particles such as virus, bacterial or the like. Further, the present invention relates to a method of producing a filtering material of the foregoing type.
2. Description of the Prior Art
The applicant common to the present invention has already made proposals with respect to a method of producing a novel filtering material for capturing very fine foreign material such as virus or the like under Japanese Patent Applications Nos. 278487/1990, 29301/1991 and 163903/1991.
Each of the proposed methods is practiced by way of the steps of preparing an aqueous treatment solution by dispersively dissolving a predetermined quantity of porous apatite particles and a predetermined quantity of water soluble glucan in water, dipping a sheet-shaped raw material in the aqueous treatment solution or spraying the latter over a sheet-shaped raw material or bringing a roller wetted with the aqueous treatment solution in contact with a sheet-shaped raw material, and drying the sheet-shaped raw material coated with the aqueous treatment solution while the porous apatite particles are included in the sheet-shaped raw material with the aid of the water soluble glucan serving as a binder.
Another method of the foregoing type proposed by the applicant is practiced by way of the steps of preparing an aqueous preliminary treatment solution by dissolving only water soluble glucan in water, allowing the preliminary treatment solution to adhere to a sheet-shaped raw material, thereafter, allowing porous apatite particles to adhere to the sheet-shaped raw material before the preliminary treatment solution is completely dried, and finally, drying the sheet-shaped raw material including the porous apatite particles with the aid of the water soluble glucan serving as a binder.
A characterizing feature of any one of the methods of the foregoing type each proposed by the applicant consists in that porous apatite particles composed of a kind of calcium phosphate particles are bonded to a sheet-shaped raw material with the aid of water soluble glucan serving as a binder.
In contrast with a conventional filtering material, a filtering material produced by employing each of the methods proposed by the applicant exhibits amazingly excellent properties of adsorbing and filtering very fine infectious or antigeneous foreign material such as virus, pollen or the like unattainable with the conventional filtering material. In the circumstances as mentioned above, the filtering material produced by employing each of the aforementioned proposed methods does not exhibit anything basically inconvenient for filter's users.
However, due to the fact that porous apatite particles are bonded to a sheet-shaped raw material via water soluble glucan, when a filtering material is practically used while it is dipped in water or it is wetted with water during practical use, the water soluble glucan is dissolved in water, resulting in the apatite particles being disconnected from the sheet-shaped raw material. For this reason, the filtering material can not be used under the aforementioned circumstances.
In addition, when the filtering material is used in an environment having a high content of moisture, the water soluble glucan absorbs the moisture, causing the surface of each porous apatite particle to be covered with the water soluble glucan. Otherwise, the surface of the filtering material becomes sticky.
When filtering materials are stored in an environment having some storage moisture, some mold appears and grows on the surface of each filtering material. Otherwise, the filtering material may transform undesirably.